Glucose monitoring systems for patients afflicted with diabetes may incorporate various functionalities, including a capability to project or predict alarms to warn patients and/or provide information related to expected glucose levels, for example. Various factors may affect glucose levels; however, glucose monitoring systems generally only have access to certain types of information and factors (i.e., the monitored information). Thus, the projected alarms generated by such glucose monitoring systems are based on limited data and, although quite helpful, may be less reliable than if additional relevant information and factors were taken into account in projecting the alarms.
In a continuous glucose management (“CGM”) system, it is possible to predict if the glucose level is going to cross a hypoglycemic or hyperglycemic threshold in the future by using the CGM data. One way to do this is to estimate the rate-of-change of the glucose and project from the latest glucose point to some time in the future. While this projected alarm is helpful, there can be a significant number of false alarms and misdetections. These often occur when the glucose level of the patient changes direction, which often occurs. These changes are caused by physiological effects (the body's production of insulin), insulin boluses, meal intake, exercise, and other causes.
In the past, continuous glucose monitoring and continuous insulin delivery are accomplished by different pieces of hardware devices that do not share data. Each device provides real time management tools for diabetes and insulin delivery respectively. With the convergence of continuous glucose monitoring and insulin pumps, real-time management tools could be developed that will enhance the existing tools and provide new real-time management functionalities that did not exist before.
For example, the FreeStyle Navigator® system from Abbott Diabetes Care Inc, Alameda, Calif., a continuous glucose monitor, provides a projected low glucose (hypoglycemia) alarm function using the trend of the glucose profile and the rate of change of glucose to predict when the glucose reading would fall below the low threshold that can be set by the user. The user can set the alarm sensitivity to receive a warning of up to thirty minutes prior to the low glucose event. With the addition of insulin delivery data, for example, the “insulin on board” information from the insulin pump, then we would be able to enhance the reliability of the projected low glucose alarm to be provided earlier and provide a tool for the user to figure out the amount of carbohydrates to take to prevent the low blood glucose from occurring.
As used herein, the term “exogenous” data is meant to encompass measurements other than glucose measurements.
On the other hand, many therapy parameters that govern the real time bolus decision using the insulin pump can be better adjusted and refined with the availability of the continuous glucose information. For example, many smart pumps today provide a way to calculate the amount of insulin to cover a food or meal event through the use of the carbohydrate ratio (also referred to as “carb ratio” herein) and the bolus calculator. However, the precise carbohydrate ratio to use is an empirically derived number. With the continuous glucose data available, the “accuracy” of the carbohydrate ratio used for a food bolus calculation may be assessed in real time to provide adjustment guidance for refining the carbohydrate ratio for use in the subsequent food or meal event.
Hence those of skill in the art have recognized a need for increased reliability of projected glucose alarms. Those skilled in the art have also recognized the need for the instant or near-instant incorporation of exogenous data to further increase the reliability and effectiveness of projected alarms. A further need has been recognized for providing tools to more accurately control glucose levels; and further, those skilled in the art have identified a need for the use of exogenous data in fine-tuning the management of a diabetic patient's glucose control. The present invention fulfills these needs and others.